1. Field of the Invention
The present invention generally relates to plasma processing apparatuses, and more particularly to a plasma processing apparatus that is configured to process the surface of a substrate by spraying a process gas in a plasma state from the gas spray opening of a spray nozzle onto the substrate.
2. Description of the Related Art
Dry etching is frequently employed for fine processing of a semiconductor substrate or a wiring layer in a process of manufacturing semiconductor elements, for instance. In dry etching, a plasma is created by microwaves, for instance, and a specimen is etched by ions or an excited gas generated thereby.
Therefore, in some cases, it becomes a problem that ionized particles collide with and damage the semiconductor substrate. Conventionally, in order to cope with this problem, only a type of gas capable of performing etching only through chemical action is extracted and introduced into an etching chamber through a transportation tube, and etching is performed by spraying the plasma etching gas from a spray nozzle onto the surface of the specimen.
For instance, a silicon wafer placed on a work holder is etched by spraying the etching gas from the spray nozzle thereonto. At this point, most of the exhaust gas generated at the time of etching and most of the unreacted (unused) part of the etching gas are introduced into a differential exhaust chamber provided in the periphery of the spray nozzle and are exhausted to the outside.
According to a plasma processing apparatus having the above-described configuration, however, the negative pressure of the differential exhaust chamber does not cause all of the exhaust gas and the etching gas to be introduced into the differential exhaust chamber, so that a residual gas composed of part exhaust gas and part unreacted etching gas may flow out to the surface of the wafer and into the etching chamber.
Therefore, in the conventional apparatus, the outflow of the residual gas generated at the time of etching into the etching chamber has caused the problems of reduction in the rate of etching and contamination and generation of dust in the etching chamber due to deposition of a reaction byproduct.
Accordingly, it is a general object of the present invention to provide a plasma processing apparatus in which the above-described disadvantages are eliminated.
A more specific object of the present invention is to provide a plasma processing apparatus avoiding the outflow to the surface of a wafer and into an etching chamber of residual gas generated at the time of processing, and having improved exhaust efficiency.
The above objects of the present invention are achieved by a plasma processing apparatus processing a surface of a substrate by spraying a process gas in a plasma state from a gas spray opening of a spray nozzle onto the substrate, the plasma processing apparatus including: an exhaust opening for exhausting residual gas generated at a time of processing the surface of the substrate, the exhaust opening being provided at a position close to a periphery of the gas spray opening; and an air jet opening generating airflow, the air jet opening being provided surrounding the exhaust opening so as to prevent the residual gas from flowing out.
According to the above-described plasma processing apparatus, the residual gas generated at the time of processing is sucked into the exhaust opening and at the same time, part of the residual gas which part has escaped being sucked into the exhaust opening is prevented from flowing outside to the surface of the substrate and into the etching chamber by the wall of air pressure formed by the airflow around the exhaust opening. Therefore, reduction in the rate of etching and contamination and generation of dust in the processing chamber due to the deposition of a reaction byproduct caused by the outflow of the residual gas into the processing chamber are prevented with certainty.